Known level measuring instruments have an antenna, which emits or receives radar or microwaves in order to determine the filling level of a medium in a filling material container. The antenna of such a level measuring instrument is then arranged for instance inside a container.
The high frequency modules of such level measuring instruments are used for generating transmit signals, which are emitted via the antenna towards the filling material. The measuring signals received are picked up via the antenna, and evaluated using a reference signal. This reference signal can be configured as a reference pulse (leakage pulse), the shape and amplitude of which depend on the component quality of a circulator, a transmitting-/receiving coupler, or the temperature of the measuring device as well. In addition, a reflection of the antenna as such or the antenna coupling may have a negative impact on the leakage pulse, e.g. if the antenna is arranged close to the coupler (circulator), or in case of large echoes at close range.